Vectorial network analyser

ABSTRACT

A vectorial network analyzer (VNA) having at least one signal generator generating a particular RF output signal, and having n measuring ports, wherein an RF coupler is assigned to each measuring port and couples out an RF signal by running into the particular port from the outside, wherein the at least one signal generator is arranged and designed in such a manner that the latter supplies a particular RF output signal to at least one measuring port as an RF signal running out to the outside. Provision is made for an amplitude and/or a phase to be stored for the RF output signal for at least one signal generator in a retrievable manner on the basis of at least one parameter in a parameter field, wherein the RF signal generator is designed in such a manner that the latter generates the amplitude and/or phase of the RF output signal in a reproducible manner on the basis of at least this one parameter.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a vectorial network analyzer (VNA)having at least one signal generator which generates a particular RFoutput signal, and having n measuring ports, where n is an integergreater than or equal to one, wherein an RF coupler is assigned to eachmeasuring port and the RF coupler is designed in such a manner that theRF coupler couples out an RF signal b_(n) running into the particularport from the outside, wherein the at least one signal generator isarranged and designed in such a manner that the latter supplies aparticular RF output signal to at least one measuring port as an RFsignal a_(n) running out to the outside.

The invention also relates to a method for determining scatteringparameters of an electronic device under test, wherein at least oneelectromagnetic wave a_(n) running into the device under test and atleast one electromagnetic wave b_(n) propagated from the device undertest are determined and scattering parameters of the device under testare calculated in terms of amount and/or phase from the determined wavesa_(n) and b_(n), wherein the at least one electromagnetic wave b_(n)propagated from the device under test is measured by means of an RFcoupler, and wherein the at least one electromagnetic wave a_(n) runninginto the device under test is generated by at least one signalgenerator.

2. Description of Related Art

In the field of electronics, vectorial network analyzers (VNA) have formany years been used for the precise measurement of electronic linearcomponents and components of active and passive circuits or assembliesat low frequencies (as LCR meters) and in the high frequency range intothe THz range as well as the optical range. A VNA records the scatteringparameters of n-port networks (n=1, 2, . . . ), which may be convertedinto 2n-pole parameters (e.g. Z- or Y-parameters). However, in the caseof mid- and high-frequencies in particular (fast circuits, i.e.,circuits in the MHz and GHz range), these recorded measured data displayvery high measuring errors. Nowadays, these measuring errors have alsobeen immensely reduced in almost every NF device (LCR meters) by meansof mathematical methods. An associated systematic error correction inthe VNAs ensures that precise measurements of fast electroniccomponents, i.e., components in the MHz and GHz range, with exclusivelylinear transmission behavior can be carried out at all.

The measuring accuracy of VNAs depends primarily on the availability ofa method for systematic error correction and the associated calibrationstandard. In systematic error correction, within the so-calledcalibration procedure the reflection and/or transmission behavior ofdevices under test which are partially or wholly known are measured.Correction data (so-called error factors or coefficients) are obtainedfrom these measured data using special calculation methods. With thesecorrection data and a corresponding correction calculation, measureddata can be obtained for any given device under test which are free ofsystematic errors in the VNA and the input lines (miscoupling=crosstalk,mismatches=reflections).

The usual form of describing the electrical behavior of components andcircuits in high frequency technology (RF technology) is by means of thescattering parameters (also referred to as S-parameters). The scatteringparameters interrelate not currents and voltages but wavecharacteristics. This form of representation is particularly welladapted to the physical conditions of RF technology. If necessary, thesescattering parameters can be converted into other electrical networkparameters which interrelate currents and voltages.

SUMMARY OF THE INVENTION

Bearing in mind the problems and deficiencies of the prior art, it istherefore an object of the present invention to provide a vectorialnetwork analyzer having precise measurements of fast electroniccomponents, i.e., components in the MHz and GHz range, with exclusivelylinear transmission behavior.

The above and other objects, which will be apparent to those skilled inthe art, are achieved in the present invention which is directed to avectorial network analyzer (VNA) comprising at least one signalgenerator which generates a particular RF output signal, and n measuringports, where n is an integer greater than or equal to one, wherein an RFcoupler is assigned to each measuring port and couples out an RF signalb_(n) running into the particular port from the outside, wherein the atleast one signal generator is arranged and designed in such a mannerthat the latter supplies a particular RF output signal to at least onemeasuring port as an RF signal a_(n) running out to the outside, suchthat for the RF output signal of the at least one signal generator, anamplitude and/or a phase are stored retrievably in the VNA as a functionof at least one parameter in a parameter field, wherein the at least onesignal generator generates the RF output signal reproducibly inamplitude and/or phase as a function of at least this one parameter.

The at least one signal generator may include an RF synthesizer. The atleast one parameter may be a frequency of the RF output signal, anoutput power of the signal generator, an ambient temperature, or ameasuring time per frequency point, or any combination thereof. The atleast one signal generator may include a phase-locked loop (PLL).

Each RF coupler may be assigned a measuring point which measures therespective RF signal b_(n). A reference signal, comprising a quartzsignal or a quartz oscillator signal (XCO signal), and having afrequency 10 MHz, may be provided such that this signal triggers areception of RF signals b_(n) at the corresponding RF coupler. Themeasuring point may be in the form of an A/D converter.

The RF coupler may be a directional coupler, such as a line coupler.

In a second aspect, the present invention is directed to a method fordetermining scattering parameters of an electronic device under test,wherein at least one electromagnetic wave a_(n) running into the deviceunder test and at least one electromagnetic wave b_(n) propagated fromthe device under test are determined and scattering parameters of thedevice under test are calculated in terms of amount and/or phase fromthe determined waves a_(n) and b_(n), wherein the at least oneelectromagnetic wave b_(n) propagated from the device under test ismeasured by an RF coupler, and wherein the at least one electromagneticwave a_(n) running into the device under test is generated by at leastone signal generator, such that the at least one electromagnetic wavea_(n) running into the device under test is determined from a storedparameter field in which the amplitude and/or phase for theelectromagnetic wave a_(n) generated by the signal generator is storedas a function of at least one parameter which influences the generationof the signal by the signal generator, wherein at least one parameter isdetermined and the amplitude and/or phase of the electromagnetic wavea_(n) generated by the signal generator is derived from the parameterfield for this at least one parameter.

An RF synthesizer may be used as signal generator. The at least oneparameter may include a frequency of the RF output signal, an outputpower of the signal generator, an ambient temperature, or a measuringtime per frequency point, or any combination thereof.

The at least one signal generator may include a phase-locked loop (PLL)and be coupled to a reference signal, in particular a reference signalof a quartz oscillator.

BRIEF DESCRIPTION OF THE DRAWINGS

The features of the invention believed to be novel and the elementscharacteristic of the invention are set forth with particularity in theappended claims. The figures are for illustration purposes only and arenot drawn to scale. The invention itself, however, both as toorganization and method of operation, may best be understood byreference to the detailed description which follows taken in conjunctionwith the accompanying drawings in which:

FIG. 1 shows a schematic representation of an electronic device undertest in the form of a 2-port (device) with the definitions for theelectromagnetic waves a_(n) and b_(n) passing into and from the deviceunder test;

FIG. 2 shows a block diagram of a vectorial three-port network analyzerwith changeover switch and six measuring points in accordance with theprior art;

FIG. 3 shows a block diagram of a vectorial three-port network analyzerwith changeover switch and four measuring points in accordance with theprior art;

FIG. 4 shows a block diagram of a preferred embodiment of a vectorialnetwork analyzer according to the invention; and

FIG. 5 shows a signal flow diagram of error coefficients for a “port 1 ”of the vectorial network analyzer according to the invention inaccordance with FIG. 4.

DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

In describing the preferred embodiment of the present invention,reference will be made herein to FIGS. 1-5 of the drawings in which likenumerals refer to like features of the invention.

FIG. 1 shows a two-port VNA with a port 1 10 and a port 2 12 which ischaracterized by its scattering matrix [S]. The waves a₁ and a₂ are thewaves, corresponding to the waves b₁ and b₂ approaching the two-portVNA, propagating in the reverse direction. The relationship is asfollows:

$\begin{pmatrix}b_{1} \\b_{2}\end{pmatrix} = {\begin{pmatrix}S_{11} & S_{12} \\S_{21} & S_{22}\end{pmatrix}\begin{pmatrix}a_{1} \\a_{2}\end{pmatrix}}$

A linear component is adequately described through these S-parameters,which are stated in terms of frequency. In the case of a component whichdisplays nonlinear effects, on feeding a signal with the frequency f₀ toone port, signals with this fundamental frequency (f_(o)) and otherfrequencies are generated at the other ports. These can for example beharmonics with the frequencies m*f₀ (m=2, 3, 4, . . . ) or, whereseveral transmission generators are used, intermodulation products ormixed products. If one of the transmission generators is modulated, thenthe number of frequencies is correspondingly great.

The scattering parameters described above can also be usedadvantageously to describe the transmission behaviors of these nonlinearcomponents. However, it should be taken into consideration that it isnecessary to specify not only the ports but also the frequencies. Forexample, one can insert the vectorial scattering parameter value S₂₁ astransmission parameter with the input port 1 10 for the fundamental wavewith the frequency f₀ and the output port 2 12 for the harmonic with thefrequency f₁=2*f₀. The prior art for these measurements primarilyinvolves purely scalar set-ups. A number of vectorial network analyzerspossess software options which are organized so as to permitmeasurements of harmonics, intermodulations, mixed products and similar.However, these measurements are only carried out on a scalar basis andthus without any systematic error correction.

With the latest network analyzers (in some cases using additionalsoftware and hardware solutions), these nonlinear transmissionproperties of assembly elements and components are measured as avectorial value including systematic error correction. This vectorialdata is extremely important for the modelling of assembly elements suchas transistors.

“Without-Thru” is known from US 2010/0204943 A1 as an innovativesystematic error correction method for these nonlinear measurements onvectorial network analyzers. This systematic error correction methodrequires no through-connections whatsoever (Without Thru). In additionto the three reflection standards Thru, Short and Match or Load, a powersensor and a comb generator are required in order to performcalibrations.

In the prior art, all these systematic error correction methods for theprecise determination of linear and nonlinear S-parameters are carriedout on network analyzers, the majority of which have 2*n measuringpoints, where n represents the number of measuring ports. This design isshown in FIG. 2. An RF synthesizer 14 emits a sinusoidal signal which isfed via a changeover switch 16 to a port 1 18, a port 2 20 and a port 322. In the switch position III, a portion of the signal is coupled outto a first line coupler 24 and passed to a first measuring point 26.This first measuring point 26 is for example in the form of an A/Dconverter. In the case of higher frequencies, a mixer (not shown) isinstalled before the A/D converter which requires an additional localoscillator signal (LO signal). At a first output 28, a signal which isproportional to an emitted wave a₃ is fed to an evaluation unit, forexample a computer. The greater part of the wave emitted at the port 322 runs to a device under test (DUT) 30, where it is reflected and areflected signal is converted via a second line coupler 32 at a secondmeasuring point 34 and passed to the evaluation unit as a reflected waveb₃ via a second output 36. The other two ports of the first and secondline couplers 24, 32 are each terminated with a 50 ohm termination 38.

This architecture shown in FIG. 2 is among other things referred to as areflectometer concept. The numerous calibration methods which are basedon the 7-term error model require this reflectometer concept.

In modern network analyzers the changeover switch 16 is replaced by acorresponding arrangement of RF synthesizers, i.e., each measuring port18, 20, 22 is controlled by its own synthesizer.

An architecture which requires significantly less investment in hardwareis represented in FIG. 3, wherein parts with the same function areidentified with the same reference numbers as in FIG. 1, so that theycan be explained with reference to the above description of FIG. 1. Indistinction to the embodiment in accordance with FIG. 1, the first linedirectional coupler 34 is arranged upstream of the switch 16 and thecorresponding line directional couplers between the switch 16 and therespective ports 18, 20, 22 are dispensed with. The first linedirectional coupler 34 thus detects the incoming signals a₁, a₂, and a₃from the RF synthesizer 14. In this concept, only n+1 measuring pointsare required. One disadvantage of this concept is that in this case onlyone calibration method can be used. As a two-port measuring device thisinvolves a so-called SOLT (Short-Open-Load-Thru) method, also referredto as a 12-term-method. As a multi-port method it is referred to as aGSOLT-method.

Economical two-port VNAs only operate uni-directionally and thus do nothave any changeover switch 16 and only measure the forwards parametersS₁₁ and S₂₁. These devices have two couplers and three measuring points.The reception measuring point for b₂ no longer requires a coupler.

Network analyzers have by far the greatest number of measuring pointsand are in consequence the most expensive electrical measuring devices.In the field of production engineering, in which the most economicalVNAs are used, any simplification of the VNAs is welcome as long as themeasuring quality is maintained and the device costs are reducedcorrespondingly. The advanced user of modern measuring technology wishesto be able to measure vectorial scattering parameters not only at thefundamental frequency but also with frequency conversion, with thesmallest possible investment in terms of costs and if possible in realtime. However, known solutions for frequency-converting measurements areunacceptably slow in terms of the measuring time. On the other hand,many measurements, for example the vectorial PIM measurement todetermine the location of a fault, do not offer the measuring accuracyprovided by conventional methods. Moreover, these measurements need tobe carried out quickly. However, these cannot be realized in the desiredmanner since the local oscillator signal (LO signal) also has to bemeasured with each measurement. The frequency of the LO generator alsohas to be changed several times in order to enable the emitted,reflected and transmitted portions to be detected.

The invention is based on the problem of simplifying a vectorial networkanalyzer of the aforementioned type in terms of its mechanical andelectronic structure as well as in terms of its operation and themeasuring procedure involved. The invention is also based on the problemof accelerating a method of the aforementioned type in terms of theprocedure and at the same time achieving a high degree of accuracy.

According to the invention this problem is solved through a vectorialnetwork analyzer of the aforementioned type with the featurescharacterized in the claims.

According to the invention, in a vectorial network analyzer of theaforementioned type, for the RF output signal of at least one signalgenerator, an amplitude and/or a phase are stored retrievably in the VNAas a function of at least one parameter in a parameter field, whereinthe RF signal generator is designed such that it generates the RF outputsignal reproducibly in amplitude and/or phase as a function of at leastthis one parameter.

This has the advantage that the RF signal a_(n) output from the nthmeasuring port does not need to be measured separately, but can bederived from the parameter field in a desired accuracy. This means thata measuring point for the signals a_(n) can be dispensed with for thedetermination of scattering parameters. No reference measuring pointsare required any more, wherein at the same time the ability to calibratethe network analyzer is not restricted. This makes it possible tomeasure linear and nonlinear transmission values, in terms of amount andphase, with very low investment in terms of hardware and time. Thus, ameasurement of vectorial and frequency-converting scattering parametersfor mixers, harmonics or intermodulations, in particular, can be carriedout very quickly. The fact that only one measuring point is now requiredper measuring port means that a network analyzer can be manufacturedsignificantly more economically and in more compact form.

An RF output signal which is particularly well reproducible and stablein phase and amplitude is achieved in that the signal generator is an RFsynthesizer.

In order to determine scattering parameters in the frequency domain, theat least one parameter is a frequency of the RF output signal. Otherparameters include an output power of the signal generator, an ambienttemperature and/or a measuring time per frequency point.

An RF output signal which is reproducible in amplitude and phase isachieved in that at least one of the signal generators has aphase-locked loop (PLL).

In order to measure the RF signals b_(n) emanating from a device undertest in the direction of the measuring ports, each RF coupler isassigned a measuring point which measures the respective RF signalb_(n).

A particularly good reproducibility of sinusoidal signals at themeasuring ports is achieved in that a reference signal, in particular aquartz signal or a quartz oscillator signal (XCO signal), in particularwith the frequency 10 MHz, is provided such that this signal triggers areception of RF signals b_(n) at the corresponding RF coupler.

A particularly simple and economical VNA combined with high measuringaccuracy is achieved in that the measuring point is in the form of anA/D converter.

A particularly good and precise coupling-out of an RF signal is achievedin that at least one RF coupler is in the form of a directional coupler,in particular as a line coupler.

According to the invention, in a method of the aforementioned type atleast one electromagnetic wave a_(n) running into the device under testis determined from a stored parameter field in which the amplitudeand/or phase for the electromagnetic wave a_(n) generated by the signalgenerator is stored as a function of at least one parameter whichinfluences the generation of the signal by the signal generator, whereinat least one parameter is determined and the amplitude and/or phase ofthe electromagnetic wave a_(n) generated by the signal generator isderived from the parameter field for this at least one parameter.

This has the advantage that the RF signal a_(n) output from the nthmeasuring port does not need to be measured separately, but can bederived from the parameter field in a desired accuracy. This means thata measuring point for the signals a_(n) can be dispensed with for thedetermination of scattering parameters. No reference measuring pointsare required any more, wherein at the same time the ability to calibratethe network analyzer is not restricted. This makes it possible tomeasure linear and nonlinear transmission values, in terms of amount andphase, with very low investment in terms of hardware and time. Thus, inparticular, a measurement of vectorial and frequency-convertingscattering parameters for mixers, harmonics or intermodulations can becarried out very quickly.

An RF output signal which is particularly well reproducible and stablein phase and amplitude is achieved in that the signal generator is an RFsynthesizer.

In order to determine scattering parameters in the frequency domain, theat least one parameter is a frequency of the RF output signal. Otherparameters include an output power of the signal generator, an ambienttemperature and/or a measuring time per frequency point.

An RF output signal which is reproducible in amplitude and phase isachieved in that at least one signal generator with a phase-locked loop(PLL) is coupled with a reference signal, in particular a referencesignal of a quartz oscillator.

The preferred embodiment of a network analyzer according to theinvention shown in FIG. 4 possesses a signal generator 110, a changeoverswitch 112 and the three measuring ports “port 1” 114, “port 2” 116 and“port 3” 118. Each measuring port 114, 116, 118 is assigned an RFcoupler 120 in the form of a line coupler, wherein each RF coupler 120is connected electrically with a measuring point 122. The measuringports 114, 116 and 118 are connected with corresponding ports of anelectronic device under test 125, the scattering parameters(S-parameters) of which are to be determined. This is represented by wayof example with a scattering matrix [S]; however, the scatteringparameters of a transmission matrix or a chain matrix can also bedetermined. The term “scattering parameters” is intended to besynonymous with the elements of any matrix which describes theelectrical properties of the electronic device under test 125 withrespect to the incoming and outgoing waves a_(n) and b_(n) or whichinterrelates these waves a_(n) and b_(n) with one another. The RFcouplers 120 are arranged such that the RF coupler 120 of the nth portmeasures the nth wave b_(n) running away from the device under test 125into the respective “port n” via the measuring point 122 and outputsthis to an associated output 124, wherein n is greater than/equal to 1and n is less than/equal to N, where N is the number of measuring portsof the vectorial network analyzer. In the example shown in FIG. 4, N isequal to three.

The vectorial network analyzer according to the invention has Nmeasuring points 122, i.e., only N measuring points 122 are now requiredin order to measure an N-port device. The changeover switch 112 is forexample formed by a corresponding number (in this case three) ofconnectable synthesizers (not shown). The signal generator 110 is forexample in the form of an RF synthesizer and at least one localoscillator (mixing oscillator) 126 is provided. The local oscillator 126supplies a mixing oscillator signal f_(LO) 128 to the measuring points122. Both the local oscillator 126 and the signal generator 110 are forexample phase-locked to a reference signal f_(ref) 130 of a quartzoscillator 132 via a phase-locked loop (PLL).

The at least one signal generator 110 supplies a signal a_(n), theamplitude and phase of which are known and reproducible. Theseproperties (amplitude and phase) are determined once for the measurementof frequency-converting scattering parameters (S-parameters) as afunction of at least one parameter and are stored retrievably in aparameter field 134. The parameter field 134 of the stored signals a_(n)extends over the frequency and is optionally extended over other valuessuch as an output power of the signal generator 110, an ambienttemperature T, a measuring time t per frequency point and others. Inother words, the signals a_(n) generated by the signal generator 110 arestored in the parameter field 134 as a function of at least oneparameter. In this way, for a given or known frequency, as exemplaryparameter, one can read the wave a_(n) running to the device under test125 via the respective “port n” from the parameter field 134 withoutneeding to measure this wave a_(n) with an additional measuring point.

The output power (amplitude) of the signal generator 110 is regulatedthrough a measuring unit (power detector) which is arranged in a controlunit 136. The phase-locking of the signal generator 110 to the mixingoscillator signal f_(LO) is only possible if the divider concept and thephase frequency control are selected appropriately. Thus, modernconcepts use sigma-delta dividers which contain random generators. Suchsynthesizer architectures are not suitable for the VNA according to theinvention. The simplest usable divider concept for the VNA according tothe invention is the classic PLL construction with several loops and(adjustable) fixed dividers.

The measuring points 122 are for example in the form of analogue/digitalconverters. In order for reproducible sinusoidal signals to be presentat the measuring points 122 in the VNA according to the invention, thereception of the analogue/digital converters is triggered through thereference signal f_(ref) 130 (also referred to as a quartz or XCOsignal) of, for example, 10 MHz. The output signal of the VNA accordingto the invention is generated correctly if, on an oscilloscope which istriggered through the reference signal f_(ref) 130 of the VNA, it isalways identical for each frequency point. This property created throughthe special signal generator 110 transforms a relative measuring device(previous VNA) into an absolute measuring device (VNA according to theinvention). Previously, in known VNAs, it was acceptable for the outputsignals to fluctuate from measurement to measurement. Only therelationship between the two wave values of a reflectometer always hadto be reproducible. In contrast, in the VNA according to the inventionthe measured data must always remain reproducible as an absolute value,from calibration to measurement.

The VNA according to the invention is suitable for use for linearmeasurements, as will be explained in detail in the following. The VNAaccording to the invention satisfies the 7-term model and canconsequently support all VNA calibration methods. For a two-portapplication, a conventional double reflectometer has four measuringpoints. In the VNA according to the invention, the two referencemeasuring points are omitted. However, in order to perform thecalibration method, a measured value must be used for the referencemeasuring points. FIG. 5 shows the situation in the form of a signalflow diagram of the error coefficients with reference to the example of“port 1” 114. a_(1m) is the measured value of the reference measuringpoint, a₁ is the reproducible wave at the measuring port 1. b₁ is thewave emanating from the device under test 125. b_(1m) is the measuredvalue at the reference measuring point. E_(D) is an error coefficientwhich interrelates a_(1m) and b_(1m) (b_(1m)=E_(D)*a_(1m)) and describesa crosstalk of a_(1m). E_(F) is an error coefficient which interrelatesa_(1m) and a₁ (a₁=E_(F)*a_(1m)). E_(R) is an error coefficient whichinterrelates b₁ and b_(1m) (b_(1m)=E_(R)*b₁). E_(S) is an errorcoefficient which interrelates b₁ with a₁ (a₁=E_(S)*b₁) and describes acrosstalk of b₁. S₁₁ is a scattering parameter of the scattering matrixwhich describes an input reflection factor for the device under test 125with adapted output of the device under test 125. The reception valueb_(1m) of the sole measuring point of the VNA according to the inventiondisplays a crosstalk of a_(1m). Here, the approximation can be made thatE_(D) is zero. In practice, E_(D) is low, with values between −35 dB and−20 dB. This approximation leads to an error of a few tenths of a dB inreflection measurements. In transmission measurements, the error isscarcely expressible. However, in this case the error coefficients arereduced and simplified calibration methods can be used.

For the general case that E_(D) is not equal to zero and a₁ isreproducible, any value (e.g., 1) can be used for a_(1m). E_(F) is onlycalculated from the ratio a₁/a_(1m). For the calibration measurementwith the 50 ohm termination, E_(D) is calculated from the ratiob_(1m)/a_(1m).

If a_(1m) is defined as any value (e.g. 1), then E_(D) and E_(F) do notcorrespond to any physical transmission values. Nor is this necessary inpractice. If the VNA according to the invention is only used for linearmeasurements, then it is not necessary to know the wave a₁. Anylimitation in the measuring accuracy of the network analyzer dependssolely on the reproducibility of the generator signals. However, withthe correct design, this is very high with RF electronics.

The VNA according to the invention is also suitable for use fornonlinear measurements, as will be explained in detail in the following.For nonlinear measurements, the first big difference in comparison withthe prior art is the fact that a measuring point for a comb generatormeasurement is no longer necessary. The hardware corresponds to that ofthe VNA according to the invention for linear measurements. Generally,any known calibration method for frequency-converting measurements canbe performed with the VNA according to the invention, setting themeasured data of the reference measuring points to a fixed value.However, the high reproducibility of the signal generators 110 offersnew possibilities. Thus, the VNA according to the invention now onlyneeds to be calibrated once, in a completely frequency-convertingmanner, at measuring adaptors (before the measuring cables). Because oftheir reciprocity, the errors in the linear measuring cables can becalibrated out individually with a standard calibration method used inlinear measuring technology (e.g., MSO).

The present invention allows a VNA to be realized, using only onemeasuring point per measuring port, which can measure linear andnonlinear scattering parameters (S-parameters). It is thus possible,with a reduction in hardware in comparison with the prior art, to use aVNA for the measurement of linear components as well as for themeasurement of nonlinear components. The omission of the referencemeasuring points means that fewer measurements have to be carried out,which results in a faster measuring time. This effect is particularlyevident with frequency-converting measurements. These can be carried outin real time with this new architecture (n-measuring point concept). Thehardware requirements for the linear device and the frequency-convertingdevice are substantially identical.

The principle of network analysis can be applied in many other fields.These include, among others, radar technology, filling-level measurementand humidity measurement. These listed measurements are often carriedout in the open using antennas. A calibration can be carried out infront of the antenna or in the open. The measuring accuracy is improvedin comparison with known solutions through the reduction in thenecessary hardware. For example, a current FMCW radar has one measuringpoint and cannot be calibrated like a VNA. With the present invention, aradar also has only one measuring point. In this case, the crosstalkfrom the transmitter to the one measuring point can be calculated out.Whereas an FMCW radar only measures the real part of the transmissionfunction, a radar device equipped with the present invention can measurethe complex transmission function and thus displays a significantlyhigher measuring accuracy.

In a method according to the invention, the wave a₁ is no longermeasured, as is usual in the prior art, but read from the parameterfield 134. For this purpose, at least one parameter is first determinedby the control unit 136 which has an influence on the generation of thewave a₁ through the signal generator 110. These are, for example, afrequency adjusted on the signal generator 110 and, optionally, otherparameters such as the output power set on the signal generator 110and/or the ambient temperature T. With this or these parameters, desiredvalues for the wave a₁, such as the amplitude and/or phase, are thenread from the parameter field 134. For this purpose, a value foramplitude and/or phase for the wave a₁ is stored unequivocally in theparameter field 134 for each value of the parameter(s). These values foramplitude and/or phase for the wave a₁ are then used for the furthercalculation of, for example, the scattering parameters S₁₁ of thescattering matrix.

The parameter field 134 only needs to be created once for the signalgenerator. For this purpose, the values for amplitude and/or phase aredetermined once, by measurement, for different values of at least oneparameter and are stored in the parameter field 134.

In the case of frequency-converting measurements, such as vectorial PIM,the network analyzer is only calibrated once on a fullyfrequency-converting basis. Thereafter, only a standard calibration(such as MSO) takes place for the purpose of measuring cablecalculation. A measuring point for a phase error of the local oscillator126 is no longer required for frequency-converting measurements.

While the present invention has been particularly described, inconjunction with a specific preferred embodiment, it is evident thatmany alternatives, modifications and variations will be apparent tothose skilled in the art in light of the foregoing description. It istherefore contemplated that the appended claims will embrace any suchalternatives, modifications and variations as falling within the truescope and spirit of the present invention.

Thus, having described the invention, what is claimed is:
 1. A vectorialnetwork analyzer (VNA) for determining scattering parameters of anelectronic device under test comprising at least one signal generatorwhich generates a particular RF output signal, and n measuring ports,where n is an integer greater than or equal to one, wherein an RFcoupler is assigned to each measuring port and couples out an RF signalb_(n) running into the particular port from the outside, wherein the atleast one signal generator is arranged and designed in such a mannerthat the latter supplies a particular RF output signal to at least onemeasuring port as an RF signal a_(n) running out to the outside, whereinfor the RF output signal of said at least one signal generator, anamplitude and/or a phase are stored retrievably in the VNA as a functionof at least one parameter in a parameter field such that the RF signala_(n) does not need to be measured separately, but can be derived fromthe parameter field, wherein the at least one signal generator generatesthe RF output signal reproducibly in amplitude and/or phase as afunction of at least this one parameter, wherein the at least one signalgenerator is coupled to a reference signal of a quartz oscillator. 2.The vectorial network analyzer of claim 1 wherein the at least onesignal generator includes an RF synthesizer.
 3. The vectorial networkanalyzer of claim 1 wherein the at least one parameter is a frequency ofthe RF output signal, an output power of the at least one signalgenerator, an ambient temperature, or a measuring time per frequencypoint, or any combination thereof.
 4. The vectorial network analyzer ofclaim 1, wherein said at least one signal generator has a phase-lockedloop (PLL).
 5. The vectorial network analyzer of claim 1, wherein eachRF coupler is assigned a measuring point which measures the respectiveRF signal b_(n).
 6. The vectorial network analyzer of claim 5 whereinthe reference signal having a frequency of 10 MHz is provided such thatthis signal triggers a reception of RF signals b_(n) at thecorresponding RF coupler.
 7. The vectorial network analyzer of claim 6wherein the measuring point is in the form of an A/D converter.
 8. Thevectorial network analyzer of claim 7 wherein said RF coupler is adirectional coupler.
 9. The vectorial network analyzer of claim 5wherein the measuring point is in the form of an A/D converter.
 10. Thevectorial network analyzer of claim 1 wherein said RF coupler is adirectional coupler.
 11. The vectorial network analyzer of claim 10wherein said RF coupler is a line coupler.
 12. The vectorial networkanalyzer of claim 1 wherein the at least one parameter is a frequency ofthe RF output signal, an output power of the signal generator, anambient temperature, or a measuring time per frequency point, or anycombination thereof.
 13. The vectorial network analyzer of claim 12,wherein said at least one signal generator has a phase-locked loop(PLL).
 14. The vectorial network analyzer of claim 12, wherein each RFcoupler is assigned a measuring point which measures the respective RFsignal b_(n).
 15. The vectorial network analyzer of claim 14 wherein thereference signal having a frequency of 10 MHz is provided such that thissignal triggers a reception of RF signals b_(n) at the corresponding RFcoupler.